Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Atomic-S on 27/08/2016 05:02:01
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In the interest of reducing the costs of space flight, it would seem advantageous if spacecraft to Mars could land in the manner or a space shuttle. However, Mars has a much thinner atmosphere. Is there any way to do this?
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Extremely large wing area, and a very high landing speed on a very smooth runway.
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Arrestor wires like you have on an aircraft carrier or stol/vstol craft?
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Another problem with Mars is that the atmosphere is too thin to do effective atmospheric braking from interplanetary speeds.
You would need to use something like rockets or a hypersonic parachute to slow the plane down to merely supersonic speeds. If you had large wings when you hit the atmosphere at hypersonic speeds, the wings would be ripped off.
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Extremely large wing area, and a very high landing speed on a very smooth runway.
Rough comparison of aircraft on Mars vs earth.
For a wing the lift at a particular velocity is proportional to air density. So we can assume that for a wing on earth with air density 1.2 kg/m3 the lift would be proportionately less on Mars with density 0.02 kg/m3 So on Mars the lift is only 0.17 that on earth.
However, gravity on Mars is less 3.7 m/s2 vs 9.8 on Earth so less to lift, reduced to 0.38 of that on earth.
So if I assume lift is proportional to wing area the wing needs to be just over twice as big, approx 2.2 times larger.
However, larger wing = more weight hence even bigger wing or as Evan says higher landing speed. Not sure what lift to weight ratio is for a typical wing so haven't attempted to estimate realistic size, but extremely big sounds about right Evan [:)].
Edit: this is only for landing or flight close to the surface. Looking at surface atmospheric pressure this is not going to be a high flyer.
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Retractable kevlar or similar wings? Maybe carbon nanotube construction. Also a possibility synthetic spider web material.
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Retractable kevlar or similar wings? Maybe carbon nanotube construction. Also a possibility synthetic spider web material.
I was wondering titanium framework.
Certainly a battle with strength vs size.
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Alan may be better placed to judge.
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Alan may be better placed to judge.
Yes, I was hoping he might join in. I'm wondering about aspect ratio, high ratio would give good lift vs drag but increase in length would give strength problems because of greater cantilever. I don't think manoeuvrability is an issue.
Do you think a hang glider type arrangement would work? Arms deploy when enough air density with a Kevlar type fabric as you suggested.
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Alan may be better placed to judge.
Yes, I was hoping he might join in. I'm wondering about aspect ratio, high ratio would give good lift vs drag but increase in length would give strength problems because of greater cantilever. I don't think manoeuvrability is an issue.
Do you think a hang glider type arrangement would work? Arms deploy when enough air density with a Kevlar type fabric as you suggested.
I'm not sure. Sorry I can't be more definite.
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Any way to maximize the ground effect of compressing the air between the ground and the wing as the craft hovers very close to the ground?
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You would need to use something like rockets or a hypersonic parachute to slow the plane down to merely supersonic speeds. If you had large wings when you hit the atmosphere at hypersonic speeds, the wings would be ripped off.
I imagine you're right. When the Curiosity rover landed, it did so in part using a parachute. I would suppose that the parachute would remain an important part of any landing system.
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When the space shuttle returned from orbit, the first thing it encountered was high temperature due to its high speed through the atmosphere. That is likely to remain an issue at Mars also. The Curiosity mission used a heat shield that was jettisoned so that its weight was no longer a problem subsequently. The shuttle, however, did not use a disposable heat shield, which saved costs but would be a weight issue.